1. Field of the Invention
The present invention relates to a tube support device that is not a baffle for use within a heat exchanger. Specifically, the invention includes interlocking plates forming a cross member grid with square shaped openings each capable of supporting a single tube. A u-shaped nodule is provided along each plate within each square-shaped opening so as to contact the tube in an unsymmetric fashion.
2. Description of the Related Art
As shown in FIG. 1, a typical shell and tube heat exchanger is comprised of a bundle of closely spaced tubes 12, referred to as a tube bundle 16, surrounded by and housed within a shell structure. The tube bundle 16 is supported at opposite ends by a first tubesheet 10 and a second tubesheet 11. Tubesheets 10 and 11 are welded to a cylinder about the tube bundle 16 so as to form the leakproof shell structure. Tubes 12 function as a conduit through which a primary fluid passes. A secondary fluid fills the interior volume of the shell and contacts the exterior of the tubes 12 so as to heat or cool the primary fluid while avoiding mixture between the two fluids.
Tube supports for use within shell and tube heat exchangers are described and claimed in the related arts. Designs address several problems common to shell and tube heat exchangers, namely, inadequate support of the tube bundle, tube vibrations, vibration induced contact between tubes, pressure loss across the shell, and construction complexity and cost.
A widely common tube support device is a baffle plate having holes through the thickness of the plate. Each hole is dimensioned so as to provide a clearance fit between plate and tube. The primary deficiency of such devices is the promotion of cross flow which in turn causes and/or exacerbates flow induced vibration.
Massy et al., U.S. Pat. No. 3,600,792, describes a tube support structure having horizontally and vertically disposed plates interlocked at a right angle so as to form a parallelepipedal opening. The “egg crate” support, as it is commonly referred to, limits contact to at most two plates and the tube within each opening. As such, Massey allows limited vibration and movement of tubes within the tube bundle. This movement may allow repeated and uncontrolled contact between tube and plates resulting in tube failure.
Williams, U.S. Pat. No. 4,579,304, and Romanos, U.S. Pat. No. 3,420,297, describe other “egg crate” supports composed of parallel disposed plates interlocked at an obtuse angle so as to form a parallelogram-shaped opening. Williams and Romanos improve the longitudinal flow of fluid within the shell and reduce pressure loss across the support. Unlike Massy, Williams and Romanos provide contact between the four plates comprising the opening and the tube there through. However, this contact greatly increases the likelihood of binding between support structure and tubes during assembly and during expansion and contraction of the tubes in use. As such, damage to and failure of tubes is more likely during assembly and operation of the heat exchanger.
Jabsen, U.S. Pat. No. 4,359,088, and Roffler, U.S. Pat. No. 4,160,477, describe two additional “egg crate” supports comprised of metal strips arranged to form a hexagonal opening. In Jabsen, a circular or rectangular dimple along each plate insures contact between each plate about the hexagonal opening and the tube there through. In Roffler, a spring tab is provided along at least four plates about the hexagonal opening so as to contact the tube there through. Jabsen and Roffler provide numerous advantages including decreased pressure drop across the tube support structure, decreased vibration of tubes, reduced buildup of impurities between tube and plates, better flow and distribution of fluid, and a slidable grip between tube support and tubes so as to accommodate thermal expansion. However, Jabsen and Roffler, as well as Williams and Romanos, increase the spacing between tubes and therefore provide for fewer tubes within a tube bundle as compared to Massy.
Furthermore, baffle plates and the “egg crates” described by Massy, Williams, Romanos, Jabsen, and Roffler frustrate axial flow of the shell side fluid through the tube bundle. As such, the related arts do not optimize heat transfer within presently known shell and tube heat exchangers.
What is required is a tube support device that reduces the vibration of individual tubes, reduces vibration induced contact between tubes, minimizes the pressure drop across the support structure, and minimizes fabrication and assembly costs.
Furthermore, what is required is a tube support device that maximizes tube density within a tube bundle.
Furthermore, what is required is a tube support device that facilitates axial flow of shell side fluid through a tube bundle.